Problem with drawing update.

Hello guys.
I'm trying to make a drawing in a window change his size every time i hit 'b' in my keyboard, but is not working properly.
Every time i hit 'b', "glVertex3f(x,y,z)" in "renderPrimitive()"function recieves new values for x and y and may drawing gets bigger. This is working fine, but my drawing gets bigger only if i click outside of my window and click back in the window. What i have to do to solve this problem?

Code :

void renderPrimitive(void)
{
glBegin(GL_QUADS);
//spaceship is a global TAD who update his variables everytime i hit 'b', i do this in a callback.
glVertex3f(spaceship->blcx, spaceship->blcy, 0.0); // The bottom left corner
glVertex3f(spaceship->tlcx, spaceship->tlcy, 0.0); // The top left corner
glVertex3f(spaceship->trcx, spaceship->trcy, 0.0); // The top right corner
glVertex3f(spaceship->brcx, spaceship->brcy, 0.0); // The bottom right corner
glEnd();
}

I put "glutIdleFunc(display);" between "glutDisplayFunc(display);" and "glutReshapeFunc(reshape);" in "main" function, and ir works, but my window almost freezes, it gets heavy very very heavy!
I tried to put after both functions too, but same thing happened.